ACPAtmospheric Chemistry and PhysicsACPAtmos. Chem. Phys.1680-7324Copernicus PublicationsGöttingen, Germany10.5194/acp-10-2709-2010Particle characterization at the Cape Verde atmospheric observatory during the 2007 RHaMBLe intensiveMüllerK.1LehmannS.1van PinxterenD.1GnaukT.1NiedermeierN.1WiedensohlerA.1HerrmannH.11Leibniz-Institut für Troposphärenforschung e.V., Permoserstr. 15, 04318 Leipzig, Germany2303201010627092721This work is licensed under a Creative Commons Attribution 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0/This article is available from http://www.atmos-chem-phys.net/10/2709/2010/acp-10-2709-2010.htmlThe full text article is available as a PDF file from http://www.atmos-chem-phys.net/10/2709/2010/acp-10-2709-2010.pdf

The chemical characterization of filter high volume (HV) and Berner impactor
(BI) samples PM during RHaMBLe (Reactive Halogens in the Marine Boundary
Layer) 2007 shows that the Cape Verde aerosol particles are mainly composed
of sea salt, mineral dust and associated water. Minor components are
nss-salts, OC and EC. The influence from the African continent on the
aerosol constitution was generally small but air masses which came from
south-western Europe crossing the Canary Islands transported dust to the
sampling site together with other loadings. The mean mass concentration was
determined for PM<sub>10</sub> to 17 &mu;g/m<sup>3</sup> from impactor samples and to
24.2 &mu;g/m<sup>3</sup> from HV filter samples. Non sea salt (nss) components
of PM were found in the submicron fractions and nitrate in the coarse
mode fraction. Bromide was found in all samples with much depleted
concentrations in the range 1–8 ng/m<sup>3</sup> compared to fresh sea salt
aerosol indicating intense atmospheric halogen chemistry. Loss of bromide by
ozone reaction during long sampling time is supposed and resulted totally in
82&plusmn;12% in coarse mode impactor samples and in filter samples in
88&plusmn;6% bromide deficits. A chloride deficit was determined to 8%
and 1% for the coarse mode particles (3.5–10 &mu;m; 1.2–3.5 &mu;m)
and to 21% for filter samples.
<br><br>
During 14 May with high mineral dust loads also the maximum of OC
(1.71&mu;g/m<sup>3</sup>) and EC (1.25 &mu;g/m<sup>3</sup>) was measured. The minimum of TC
(0.25 &mu;g/m<sup>3</sup>) was detected during the period 25 to 27 May when pure
marine air masses arrived. The concentrations of carbonaceous material
decrease with increasing particle size from 60% for the ultra fine
particles to 2.5% in coarse mode PM.
<br><br>
Total iron (dust vs. non-dust: 0.53 vs. 0.06 &mu;g m<sup>3</sup>), calcium (0.22
vs. 0.03 &mu;g m<sup>3</sup>) and potassium (0.33 vs. 0.02 &mu;g m<sup>3</sup>) were found as
good indicators for dust periods because of their heavily increased
concentration in the 1.2 to 3.5 &mu;m fraction as compared to their
concentration during the non-dust periods. For the organic constituents,
oxalate (78–151 ng/m<sup>3</sup>) and methanesulfonic acid (MSA, 25–100 ng/m<sup>3</sup>)
are the major compounds identified. A good correlation between
nss-sulphate and MSA was found for the majority of days indicating active
DMS chemistry and low anthropogenic influences.